Speaking Up for Science and the Need to Protect Our Herd Immunity

A unified coalition of health care professionals and community advocates from throughout Arizona are  speaking up to strongly oppose two  sets of vaccine related bills currently under consideration in the Arizona Legislature.   (HB 2470, 2471, 2472 and SB1114, 1115, 1116).

Vaccination is one of the cornerstones of preventing disease and improving the health of our society. 

They are speaking out and you can too.

Did you know that when you and your children get vaccinated, you’re protecting yourself and your community? It’s called herd immunity. Here in Arizona communities  are already falling below the safety levels for the MMR Vaccine at a time when Measles outbreaks are just a short plane ride away. (See the map.)

Bob England, MD, MPH, former director of the Maricopa County Department of Public Health (2006-2018) shared the following Op Ed on AzBig Media last week:

Metro Phoenix is currently the single location in the U..S most susceptible to a large, sustained measles outbreak.  I don’t make that assertion lightly. 

You’ve probably heard about recent measles outbreaks in the news.   As of this writing, 7 cases in Texas, 53 cases in Washington State, 204 cases in New York, and a phenomenal 80,000 cases last year in Europe, including some 50,000 hospitalizations and at least 72 deaths.  Measles is a vaccine preventable disease that was uncommon in most of the developed world until recent years, and declared “eliminated” from the Western Hemisphere only a few years ago.  

What’s going on here?

No vaccine is perfect, but the measles component of the MMR vaccine is about as close as we come.  Two doses of measles vaccine, the first at 12-15 months of age and the second between 4 and 6 years of age, offers about 97% protection.  That means that if a vaccinated person is directly exposed to the measles virus, there is only a 3% chance that he or she will become infected.  Even if a person with measles walks amongst us, as long as nearly everyone is vaccinated, it is much harder for the virus to find another person to infect.  And if it does find another person or two to make ill, it is hard for it to spread any further.

That’s called “herd immunity,” and that’s what really keeps outbreaks from happening.  Each of us will likely never know whether our own vaccine worked to protect us, because we’ll never be exposed in the first place.  Herd immunity greatly amplifies the effect of vaccines, and in fact provides protection even for those who cannot be vaccinated, such as immunosuppressed cancer patients, or infants too young to get their first dose of vaccine.

Because of herd immunity, measles, a disease which once infected a half million Americans each year, mostly children, and killed several hundred annually, became virtually unknown in this country – until recently.

Increasing rates of parental refusal to vaccinate their kids, often based upon misrepresentations in social media, has led to lower rates of immunization in children both in Europe and in the US.  It appears from the European experience and elsewhere that a community-wide immunization rate of 95% is the approximate threshold for maintaining herd immunity against measles.  Statewide, we’ve slipped just below that, and still falling.  But Maricopa County is particularly vulnerable.

Arizona is one of only 17 states that allow parents to claim “personal beliefs” exemptions for school required immunizations.  Our rate of these non-medical exemptions has been steadily growing.  There are many schools within our community, particularly some charter schools, which have kindergarten immunization rates of 50% or lower.  If a case of measles entered any of those schools, there would be an explosive outbreak.  That much we know for sure.

But worse, and more fearful, is the possibility that if that happens, a sustained community outbreak could result in metro Phoenix.  Such an outbreak would be fueled not just by the low rate of immunization occurring in small pockets in certain schools, but by the total number of susceptible children (and adults) within the broader community.  

At 4.3 million people, Maricopa County is huge.  As it turns out, when you multiply our immunization exemption rate by the total number of kindergarten school children, we have the largest number of exempted kindergarten kids in the country.  A recent study did just that, and found that we have more than triple the number of these susceptible children than the next closest community – nearly 3,000 compared to less than 1,000 in Salt Lake City. (The state of the antivaccine movement in the United States: A focused examination of nonmedical exemptions in states and counties. Olive, JK, et al., PLOS Med, J PMed. June 12, 2018)

Here’s the point.  If a single measles case lands in one of our severely under-immunized schools, causing a localized outbreak within that school, there will be several new cases, leading to ample opportunity for it to spread further.  Given our large population of unimmunized kids, we may be at greater risk for experiencing a truly large, community-wide outbreak than any other place in the US.  If that comes, and our lack of herd immunity causes an outbreak in which many of us are exposed, even some of those who have been immunized will get sick (remember, fully vaccinated persons are only 97% protected, so 3% of those exposed will probably become ill despite their own vaccine).  Think about that.

And it won’t come cheap.  Because it is so wildly infectious, measles outbreaks are the most intense and expensive outbreaks that public health departments and the medical community generally face.  The public cost alone to Maricopa County of just two cases in recent years was more than $120,000. (Cost Analysis of 3 Concurrent Public Health Response Events: Financial Impact of Measles Outbreak, Super Bowl Surveillance, and Ebola Surveillance in Maricopa County.  McCullough, JM, et al., Journal of Public Health Management and Practice: June 20, 2018.)  A major outbreak leading to hundreds of cases, as seen in Europe, will cost this community many millions of dollars.

Herd immunity is nothing short of a medical miracle.  What truly protects you right now is not so much the vaccine you got as the vaccines that everyone around you got.  And being immunized, and immunizing your children, doesn’t just protect you.  It helps protect the entire community, including those most vulnerable.

Nothing screams that we’re all in this life together quite like the miracle of herd immunity.  And nothing will demonstrate just how foolish we are as a society like a needless, major measles epidemic more than half a century after the development of a safe and effective vaccine.  

Dr. England is not alone in his concerns.  The letter below was delivered to all members of the Arizona House of Representatives on February 12, 2019.  A second letter, referencing SB1114, SB1115, and SB1116, was delivered to all Senate offices.


On behalf of a unified coalition of health care professionals and community advocates from throughout Arizona, we are writing to strongly oppose the trio of vaccine related bills currently under consideration in the Arizona House of Representatives (HB 2470, 2471, and 2472). Given that vaccination is one of the cornerstones of preventing disease and improving the health of our society, we would like to register our strongest possible opposition to these bills. 

Along with sanitation, clean food and water, and antibiotics, vaccination stands as one of the most important pillars of health improvement for the human species in our entire history. Diseases such as smallpox, polio, and diphtheria that in previous times killed and maimed thousands of people are now relegated to the history books. We should be doing everything we can to promote vaccination in as many people as possible, to preserve herd immunity (or community immunity). Herd immunity is the community protection that vaccines offer when at least 95% of the population is vaccinated. If the vaccination rate falls below that threshold, the community is at risk of disease spreading to those too young or sick to be vaccinated.  

Which is why the three bills under consideration are so disturbing. HB 2470 seems to extend the concept of personal exemptions to vaccinations to include religious exemptions. No major religion opposes vaccinations, and clearly any religious concerns would already fall under the personal exemption language. Today, we see dangerous outbreaks of measles because of “exemptions” to vaccinations. As a matter of public safety, we should not be promoting more ways to avoid immunization. Allowing herd immunity to drop enough to let outbreaks occur is a severe danger to public health.

The clear intention of HB 2471 is to scare parents and reduce the number of vaccinations by requiring as much information as possible be provided regarding the extraordinarily low rate of adverse effects. Vaccines are one of the safest health interventions we have in all of health care. From the perspective of public health and policy, the emphasis on the minute chance of significant adverse events is not helpful. A Vaccine Information Sheet is already provided to parents with each vaccination, so adding an additional documentation burden provides only harm to the citizens of Arizona.

HB 2472 suggests that antibody titer tests should be offered as reasonable alternatives to vaccination. This idea betrays a profound misunderstanding of the immunology of vaccinations, the concept of herd immunity, and the immunobiology of infants. First, the majority of vaccinations need to be given within the first year of life. Antibody titers during this period are useless, due to the presence of maternal antibodies in the infant’s blood. A positive titer in these children means nothing regarding the child’s own immunity. Second, the accuracy and utility of these titers in older patients is also not clear. Third, delaying or preventing immunizations in patients while titer tests are attempted to be arranged and possibly not even done is just bad policy. Even in the presence of a positive titer, it would not be bad from a public health perspective to administer the vaccine. Maximizing immunization rates should be our goal. We want to prevent dangerous diseases and save lives.

The bottom line is this: the World Health Organization lists reduction in immunization rates and loss of herd immunity as one of the top ten threats to public health in the world. The above legislation does nothing to reduce that threat, and everything to increase it.  With rates of unimmunized children in Arizona already above 5%, we are in danger of breaching the basic societal contract we owe to each other to become vaccinated and establish a necessary herd immunity. For the lives of our citizens, we need to be implementing legislation that increases immunization rates, not reduces them. We, as advocates for patient and societal health, implore you not to lead Arizona to the bottom and contribute to the spread of untold disease and human suffering.  Thank you for hearing our plea.


Traci Pritchard, MD, FACR, President, Arizona Medical Association
A.D. Jacobson, MD, FAAP, Steering Committee Chair, The Arizona Partnership for Immunization
Laura Dearing, Executive Director, Arizona Academy of Family Physicians
Angela DeRosa, DO, MBA, CPE, President, Arizona Osteopathic Medical Association
Gretchen Hull, MD, President, AZ Chapter the American Academy of Pediatrics
Robert Aaronson, MD, FACP, Governor, American College of Physicians Arizona Chapter
Greg Vidor, President/CEO, Arizona Hospital and Healthcare Association
Casey Solem, MD, FACEP, President, Arizona College of Emergency Physicians
Mona Amini, MD, MBA, FAPA, President, Arizona Psychiatric Society
Kirsten J. Bonnin, M.M.S., PA-C, President-Elect, Arizona State Association of Physician Assistants
Will Humble, MPH, Executive Director, Arizona Public Health Association
Woodrow A. Myers Jr., MD, Chief Medical Officer & Chief Healthcare Strategist, Blue Cross® Blue Shield® of Arizona
Breann Westmore. Director Maternal Child Health & Government Affairs, March of Dimes – Arizona Chapter
John McDonald, Chief Executive Officer, Arizona Alliance for Community Health Centers
Glenn Hamer, President, Arizona Chamber of Commerce and Industry
Jennifer Carusetta, Executive Director, Health System Alliance of Arizona 
Joan Koerber Walker, President and Chief Executive Officer, Arizona BioIndustry Association, Inc. (AZBio)
Scott Lick, MD, President, Pima County Medical Society
Kelly Fine, RPh, FAzPA, Chief Executive Officer, Arizona Pharmacy Association
James Carland, MD, President/ Chief Executive Officer, MICA
Lucinda Harris, MD, President, Phoenix Society of Gastroenterology

Your voice  matters.  

Reach out to your legislators and ask them to protect our community from preventable diseases and to  please oppose:

HB2470 schools; immunization; religious exemption
HB2471 informed consent; vaccinations.
HB2472 vaccinations; antibody titer testing; notification

SB1114 schools; immunization; religious exemption. – Oppose – S Education Tuesday 2/19, 2 PM
SB1115 informed consent; vaccinations- Oppose
SB1116 vaccinations; antibody titer testing; notification.- Oppose

How to find or contact your Legislators:

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Posted in Advocacy and Regulations, AZBio News.